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(11) | EP 4 236 111 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | PHASE NOISE TOLERANT COHERENT MODULATION FORMATS FOR SHORT REACH OPTICAL COMMUNICATION SYSTEMS |
| (57) Systems and methods are disclosed herein for coherently modulating and demodulating
coherent optical signals using 5-bit constellations. The 5-bit constellations have
improved suitability for short reach optical communications systems. A first 5-bit
constellation can be formed from four rings. The first and fourth rings can form quadrature
phase-shift keyed four-symbol sub-constellations, and the second and third rings can
form phase-shift keyed twelve symbol constellations. Symbols from the third and fourth
sub-constellations are arranged to form a square. A second 5-bit constellation can
include an inner 16 symbol sub-constellation and a sixteen symbol outer sub-constellation.
Each of the symbols of the inner sub-constellation are equally spaced from its nearest
neighboring symbols along both the quadrature and in-phase axes. Each of the symbols
in the outer constellation has an equal euclidean-distance with its nearest neighboring
symbols in the outer sub-constellation.
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